Determination of the efficiency of oxidative phosphorylation in continuous cultures of Aerobacter aerogenes

Abstract

For anaerobic glucose-limited chemostat cultures of Aerobacter aerogenes a values of 14.0 g/mole was found for Ymax/ATP and a value of 6.8 mmoles ATP/g dry weight/hr for the maintenance coefficient. Both values are much lower than those previously determined for tryptophan-limited anaerobic chemostat cultures. It is concluded that generally the largest part of the maintenance energy is not used for true maintenance processes. For aerobic glucose-limited chemostat cultures two phases could be differentiated. Acetate production started at mu values higher than 0.53. The slopes of the curves relating the specific rates of glucose- and oxygen consumption with mu became higher and lower respectively above the mu value of 0.53. Using the YATP values obtained in the anaerobic experiment a P/O ratio of about 1.3 could be calculated for glucose- and tryptophan-limited chemostat cultures. In sulfate-limited chemostat cultures acetate was produced at all growth rates. At high growth rates also pyruvate and alpha-ketoglutarate were produced. With the YATP values obtained in the anaerobic experiment a P/O ratio of about 0.4 was calculated for sulfate-limited chemostat cultures.